Analysis of GSM air interface using DVB-T receiver and GNU radio

摘要

This paper focuses on the Radio Resource (RR) layer, specifications of Global System for Mobile communications (GSM) system and studied their different information with the help of GNU Radio, RTL-SDR and Wireshark. This paper first outlines the Link Access Protocol over Dm Channel (LAPDm) followed by how RR layer is established which includes: initial access over Random Access Channel (RACH), channel activation over Base Transceiver Station (BTS), immediate assignment over Common Control Channel (CCCH) and establishing LAPDm connection. The RR channel release process and cipher mode setting are entirely explored in this paper and control channel information like ARFCN channel in use by mobile device of the particular network and IMSI number was reckoned. The content of important System Information (SI) elements like Cell Channel description, RACH control parameters and Location Area Identity (LAI) are discussed in this paper. It was also distinguished that observed cell towers used both encryption and frequency hopping.